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edit on 2006-6-13 |
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==major problems seem to be fixed==
Accuracy tag removed (thanks to Ben Standeven). Tech tag removed; subject is inherently technical. --[[User:Trovatore|Trovatore]] 02:18, 20 September 2005 (UTC)
== edit on 2006-6-13 ==
The main changes are:
* Carefully separate the cases of sets of numbers and sets of reals. This is an experiment that may be useful on [[arithmetical hierarchy]] as well.
* Emphasize the fact that this is lightface (maybe more emphasis needed?)
* I rephrased the introduction. The anlytical hierarchy is not really about second order logic; it is about higher type languages such as Z_2 or type theory in first order logic. Every use I know of is in the context of first order ZFC or first order Z_2.
* Add a reference to Rogers' book. I plan to add more references.
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